1. Field of the Invention
This invention relates generally to quenching of heat treated materials, and more particularly, to a method and apparatus for automatically determining whether the quenchant being employed is performing the quenching operation satisfactorily.
2. Description of the Prior Art
Quenching systems are known. Typical prior art quenching systems typically utilize a quenching medium such as water, oil, brine or the like, or mixtures thereof, to quench heated work pieces at predetermined quenching rates to obtain certain desired metallurgical characteristics.
While prior art quenching systems generally do produce parts or components having the desired metallurgical characteristics, the quantity of the parts being produced tends to deteriorate as the quenching medium becomes contaminated or otherwise changes or degrades. Also, when a newly designed part is first manufactured, in many instances, the determination of the proper quenchant to obtain the desired metallurgical characteristics is a matter of trial and error, and once the proper quenching medium has been established, its characteristics are still subject to the previously mentioned changes. Both of the above-mentioned factors can result in improper quenching, and the results of such improper quenching would not become apparent until the characteristics of the quenched work pieces were metallurgically examined. Consequently, many improperly quenched components could be manufactured before the improper quenching was detected.
Because the purpose of quenching is to obtain certain desired phases in the quenched medium, for example, austenite, bainite and pearlite in ferrous materials, the earliest prior art methods for determining whether the quenching medium was operating properly simply utilized a physical or metallurgical examination of the quenched parts being manufactured. Later systems monitored the cooling characteristics of the part being quenched and looked for a "dwell" in the cooling curve indicative of a change in phase of the material being quenched. Typical of such prior art patents are U.S. Pat. Nos. 3,981,834; 4,088,974; 4,133,036 and 4,187,541. However, such systems are more applicable to determining the cooling characteristics of the material being cooled to determine if desired transformtions had taken place, rather than to checking the performance of the quenching medium itself.